Rectifier.



No. 67l,249. Patented Apr. 2, l90l'. E. THOMSON.

RECTIFIER.

(Application filed Jan. 9, 1900., (No Model.) 2 Sheets-$heat l.

E LL 1 \A/Ttnesses. Inventor.

v I Elihu Thomson E. THOMSON.

RECTIFIER.

(Application filed Jan. 9, 1900.1 (No Model.) 2 Sheets-Sheet 2.

Patented Apr. 2; I90l.

Fig. 2.

- Witnessegs. I j Inventor" Elihu Thomson MOZL I I fi Yn: NORRIS Pawnsco, worommo. WASNINGTGN, uv c.

UNITED STATES PATENT Oturcsi ELIHU THOMSON, OF SWAMPSOOT",MASSACHUSETTS, ASSIGNOR TO THE GENERAL ELECTRIC COMPANY, OF NEW YORILREOTHFIER.

SPECIFICATION forming part of Letters Patent No. 671,249, dated April 2,1901.

Application filed January 9, 1900. Serial No. 8'73. ll lo model.)

To all whom it may concern.-

Beitknown that I, ELIHU THOMSON, a citizen of the United States,residing at Swampscott, in the county of Essex and State oflllassachusetts, have invented certain new and useful Improvements inRectifiers, (Case No. 1,087,) of which the following is a specification.

Among the difficulties to be overcome in rectifying alternating currentsis the sparking which takes place at the moment of commutation. In orderto reduce the sparking to a minimum, it is necessary that thecommutation take place at some particular point in the wave of thealternating current, this point being generally at or near the zerovalue. If the commutation takes place at other values of current, anincrease in sparking is the result. Owing to this fact a change of loadon the rectified circuit generally causes an increase in sparking, sinceit shifts the phase of the current,and therefore changes the pointin thewave at which commutation takes place. To overcome this difficulty, ithas been a common practice to adjust the brushes of the rectifier eitherby hand or by automatically-controlled means. In either case the brushadjustment is a troublesome matter, and to avoid the necessity formoving the brushes Ihave provided an apparatus in which the brushes aremaintained in a fixed position and the necessary adjustment of the pointof commutation secured by varying the angular position of the commutatordriving-shaft with respect to the alternating wave ofimpressedelectromotive force.

My invention further comprises means for avoiding the bad effects due tohunting of a synchronous drivingmotor for a rectifier.

My invention may assume many different forms as to its broad features,and for purposes of illustration I have therefore selected embodimentsof the same which I consider useful in practice; but it is to beunderstood thatin describing certain modifications which my inventionmay undergo I do not thereby intend to limit myself to the particularforms or details shown, but, on the contrary, the scope of my inventionis to be determined by reference to the claims appended hereto and notsolely by an examination of the followtator K of suitable form.

ing description and accompanying drawings, showing specific embodimentsthereof.

In the drawings, Figures 1 and 2 show modifications of a rectifyingapparatus.

In Fig. 1 a source of alternating current of the three-phase type isindicated diagrammatically at 1, this source being connected todistributing-mains 2 3 st for supplying current to translating devicesof any desired nature. The drawings show a rectifying apparatusconnected to the supply-mains 2, 3, and a; but it will be understoodthatother translating apparatus as well may derive current from the samesource. The rectifying apparatus consists ofa rectifying-commutatorsupplied from the secondary windings of a system of transformers TT T These transformers are of the three-phase type and are connectedwith their primary windings to the supplyunains 2 3 a, the secondarywindings being shown in this instance as if-connectedthat is, with oneterminal of each winding joined to a common point, (indicated at O.) Thetransformers may be of either the constant-potential or constant-currenttype; but for the present purpose I find it most desirable to constructthem to produce constant secondary current, this construction being onein which the primary and secondary coils are movable relatively to eachother in a manner well understood in the art. The drawings indicatemerely the primary and secondary windings and are not intended to showthe particular structure whereby a constant secondary current may beproduced, since the means for securing this result is well understood.The free terminals of the secondary winding are led forward andconnected to brushes bearing upon collector--1'ings 5 G 7, forming partof the rectifying apparatus. These rings are electrically connected withappropriate segments in a rectifyingcommu- The rectified current fromthis comm utator is led to translating devices, here shown as of theconstantcurrent type, such as are-lamps or the like. The collector ringsand the commutator thus referred to are of any ordinary type, and thusrequire no further description. The means whereby the commutator isdriven includes, however, some novel features.

The power for driving the commutator is obtained from a synchronousmotor, (indicated at The field of this motor may be excited from anysuitable source of direct current-such, for example, as a storagebattery B. Thearmature of the motor is wound to receive two-phasecurrents and is supplied with four collecterrings 8, 9, 10, and 11 forleading the two-phase current into the armato re. One phase, representedby the connections leading to the rings 8 9, receives cur rent directlyfrom the source of three-phase currents through leads 12 13, connected,respectively, to the mains 4: 3, while the other phase, represented bythe armature connections to the collector-rings 1O 11, receives currentfrom the secondary system of the transformers T T T This connection withthe secondaries of the transformers may be made in any suitable manner;but for the present purpose I find it desirable to supply current to thecollector-rings 10 and 11 by means of conductors leading from the freeends of the secondaries 1t and 15, as shown. As thus connected it willbe noted that the current supplied over the leads 12 and 13 to one phaseof the armature-winding of the motor has, generally speaking, a fixedphase relation with respect to the impressed electrometive forces of thesupply-mains, while the current fed into the collector-rings 10 and 11,corresponding to the other phase of the motorarmature, has a phaserelation with respect to the electromotive force impressed on the mains2 and 13, which varies with the load on the secondaries of thetransformer system, since, as is well known, the current in thesecondaries ofa transformer changes its phase relation with respect tothe primary electr0- motive force as the load changes. Thus current of agiven phase supplied over mains 12 and 13 to one phase of the motor andcurrent of a relatively-shifting phase supglied to the other phase ofthe motor produce a resultant polar line which shifts in position withrespect to the motor-armature as the load on the transformer systemvaries. This feature I take advantage of in adjusting the commutation ofthe rectifying device driven by the motor. As the load on the rectifiedcircuit, and consequently in the secondary windings of the transformersystem, varies the magnitude and phase of the current supplied from thesecondary system to the motorcorrespondingly shift, thus shifting thepolar line in the motor-armature, and, as a consequence, correspondinglyshifting the motor-armature to bring the polar line into proper positionwith respect to the exciting-field. By making suitable adjustments andproportions of these various factors the motor-armature may be caused tomove backward or forward, as the load on the rectified circuit changes,by such an amount as may be necessary to adjust the pointofcommutationof the rectifier, and thus secure minimum sparking.

I have described the transformers T, T,

and T as of the constant-current typo, in which the secondaryeloctromotive force consequently varies from zero to a maximum, thuscorrespondiugly varying the current supplied to one phase of thedriving-motor for the rectifier; but it is to be understood thattransformers of the constant-potential type may be employed by makingsuitable connections. In this latter case one of the armature-windingsof the driving-motor would be placed in series with one of the secondarymains in order to respond to change of load, since with aconstant-potential system the secondary voltage varies but little.

A feature of my inventlon to which I have not heretofore alludel is theflexible connection between the d riring-motor S and the rectifier K.This connection consists of a helical spring 16, connecting the shaft ofthe mo tor S with the shaft of the rectifier K, the lat ter beingprovided with a fiy-wheel 17 in order to secure sufficient inertia. Thespring 16 has for its object to overcome the detrimental effects due tovariations in speed of synchronous motors, known in the artas hunting.\Vhen operating in this manner, the speed of the motor surges backwardand forward from the normal with a period of oscillation and a Violencewhich depend upon many factors-such, for example, as the field strengthof the motor, the reactance of the transmission-lines, and thesteadiness or unsteadiness of the frequency of the supplied current. Ifthe spring 16 be so chosen as to have a period of oscillation differentfrom that of the period of oscillation of the motor, then these twoperiods will so far fail to combine as to produce a fairly uniformdegree of rotation of the apparatus driven through the medium of thespring. The function of the fly-wheel 17 is t store up and restoreenergy due to fiexure of the spring 16, and this flywheel or itsequivalent is necessary or at least useful in obtaining the best resultsfrom the operation of the flexible connection 16.

Another form which my invention may assume is shown in Fig. 2, in which,as before, 1 indicates a source of threcphase alternating currentshaving tram-nnissiondinos 2, I), and -t leading therefrom. The currentto be rectified is passed over leads 18, 19, and 20 to suitablecollector-rings connected in the ordinary manner to arectifying-commutator K. Erushes bear upon the commutator K and areadjusted in a certain fixed position thereon, the rectified currentbeing conducted away through conductors 21. and 2: and after passingthrough a regulating-coil 23 going to translating devices not hereinshown. The commutator K is driven by a synchrono s motor S, herein shownas of the two phase type, one phase being supplied from the secondary 24of a transformer whose primary 25 is connected to the supply-mains 2 at,while the other phase is supplied from the secondary 20 of a transformerwhose primary 27 is connected across a different pair of too mains 3 4of the three-phase supply system. The necessary adjustment of theposition of the motor-armature is secured by shifting the polar line ofthe rotating field, and this result is accomplished by varying the valueof one phase of the supply-current with respect to the other. Althoughthis does not necessarily change the phase of the respective currents,it does shift the position of the resultant field. I accomplish thischange in relative magnitude of the currents supplied to the motor byinversely-varying resistances placed in series with the secondaries 24:and 26, these resistances being shown, respectively, at 28 and 29. Tapsare brought out from each resistance and connected to suitablecontact-points arranged on arcs of circles, and these contact-pointscooperate with corresponding insulated switch-arms 30 and 31, connectedto the terminals of the transformers 24c and 26, the circuits to thearmatn re of the motor S being completed by conductors 32 and 33,leading from the ends of the resistances 28 and 29,respectively. Theswitch-arm 34 is caused to oscillate backward and forward over itscooperating contacts by means of a link-and-lever connection with a coreof magnetic material in inductive relation to the solenoid 23. A spring35 acts upon the lever 36 and serves to urge the switch-arm 34 into oneextreme position,while current flowing to the solenoid 23 by operatingupon its core causes the switch-arm to be moved in the oppositedirection. As the load in the circuit 21 22 varies it will thus be seenthat the resistances in the respective supply-circuits for the tWophases of the motor are inversely varied, thereby causing the polar lineof the resultant field to shift correspondingly with respect to thearmature. By suitably proportioning this effect the re sultant shiftingof the motor-armature may be made such as to shift therectifying-commutator backward or forward with varying load by an amountrequired to adjust the point of commutation, and so secure a minimumamount of sparking.

In Fig. 2, as in Fig. 1, the synchronous motor shown may be excited byany suitable source of direct current-such, for example, as a storagebattery B.

Instead of the resistances 28 29 any other suitable impedance mayevidently be employed.

That I claim as new, and desire to secure by Letters Patent of theUnited States, is

1. The combination of a rectifying-commutator, a motor for driving thesame and a resilient connection between the commutator and the motor.

2. The combination of a rectifying-comm utator, a motor for driving thesame and a coiled-spring connection between the commutator and themotor.

The combination of a rectifying-commutator, a multiphase motor fordriving the same, and antomatically-controlled means for adjusting theposition of the motor-armature with respect to the Wave of currentsupplied to said commutator.

4. The combination of a source of alternating current, arectifying-commutator, a multiphase motor supplied with current fromsaid source and driving said commutator, and means for changing therelative magnitudes of currents supplied to said motor.

5. The combination of a source of alternating current, arectifying-commutator, a multiphase motor supplied with current fromsaid source and driving said comm ntator, and means for automaticallychanging the rela tive magnitudes of currents supplied to said motor inaccordance with variations in magnitude of the rectified current.

6. The combination of a transformer, a rectifying-commutator connectedto the secondaryof the transformer, a multiphase motor for driving saidcommutator, connections be tween the primary supply-circuit for saidtransformer and cond uctors corresponding to one phase ofthe'supply-circuit for said motor and other connections betweenconductors corresponding to another phase of the motor supply-circuitand the secondary circuit of said transformer.

7. The combination of a rectifying-commutator, a synchronous motor fordriving the commutator, and means responsive to changes in the loadsupplied by said commutator for causing the armature of the motor tochange its angular position with respect to some given point in the waveof impressed electromotivo force.

S. The combination of a rectifying-comm utator, a synchronous motor withits armature connected to said commutator, and automatically-controlledmeans for adjusting the angular position of the armature of the motor.

9. The combination of a source of alternating current, arectifyirig-commutator, a motor supplied with current from said sourceand driving said rectifying-commutator, and means controlled by therectified current for causing the shaft carrying therectifying-commutator to change its angular position with respect tosome given point in the wave of impressed electromotive force.

10. The combination of a source of alternating current, arectifying-commutator, a motor for driving said commutator, and meansfor adjusting the angular position of the motor-armature with respect tothe phase relation thereto of the impressed electromotivc force.

In witness whereof I have hereunto set my hand this 6th day of January,1900.

ELIHU THOMSON.

Witnesses:

DUGALD MoKlLLoir, JOHN MCMANUS.

